The present invention relates to a camera provided with an aperture controllable shutter capable of controlling the size of an aperture for optimum exposure and a vari-focal lens system, e.g. a zoom lens or two-focus lens.
The aperture controllable shutter has widely been used as a lens shutter of a low-cost common camera. Such common cameras are now highly improved in the performance and some are even equipped with vari-focal lens systems such as zoom lenses. Also today's vari-focal lens systems have a broad focusing range from wide angle to telephoto.
However, when such a broad-range vari-focal lens is adopted, an aberration in peripheral areas of a photographing plane tends to increase particularly at wide-angle side, and amount of light exposure tends to be lower. For compensation, the lens system has to be designed in complicated structure, resulting in an increase in the production cost.
In this respect, a modification is proposed (as disclosed in Japanese Laid-open Patent Publication No.63-300226 in which the aperture (the diameter of an aperture) of an aperture controllable shutter is allowed to open small at the wide-angle side so that an increase in the aberration and a declination of the amount of light exposure can be minimized. More particularly, a controller member is provided for entering into the moving path of the aperture controllable shutter or its linked mechanism so that the changeable amount of the aperture (or the aperture controllable shutter) size can be restricted corresponding to a change in the focal length.
That arrangement may eliminate the foregoing drawback, but becomes bulky in size because the controller member is added for mechanical movement at each focal length variation and the lens system itself is enlarged for accommodating such a modified shutter mechanism.